Preparation and characterization of pesticide Fosthiazate‐loaded microcapsules for controlled release system

Abstract

Preparation of Fosthiazate (FTZ)-loaded microcapsules with controlled release was attempted by the interfacial polymerization using toluene diisocyanate (TDI) and triethylenetetramine (TETA) as monomers. The effects of the monomer concentration and the monomer concentration ratio on characteristics of the microcapsules such as size, shell thickness and release behavior in water and in soil were studied. In the study, FTZ was successfully encapsulated into a polyurea resin, and the characterization revealed that the microcapsule shell became thicker proportionally to the applied monomer concentration. The release rate of FTZ from the microcapsules in water was mostly proportional to the ratio of the surface area to the shell thickness of the microcapsules, and the release rate fitted the first-order kinetic model. On the one hand, when TDI concentration was low or the monomer concentration ratio was high, the release rate was significantly increased owing to the formation of insufficient microcapsule shell and the coarseness of the shell. Moreover, the slower the release rate in water was, the higher residual ratio of FTZ in soil could be maintained. However, it was also observed that the release rate in soil was faster than that in water. It is suggested that the constant replacement of water around the microcapsules accelerated the release rate, or the microcapsule particles migrated through the soil. These results indicated that FTZ-loaded microcapsules with controlled release were able to be prepared. In addition, basic findings about the relationship and the difference between the release behaviors of FTZ-loaded microcapsules in water and in soil were obtained.

Interfacial Polycondensation to Fabricate Polyurethane Microcapsules: Unraveling the Mechanism of Shell Formation and Achieving Desired Shell Thickness Based on Hansen Solubility Parameter Theory

“…This also explains why, in previous studies, when the concentration of monomers for shell material in interfacial polymerization was low, it led to a decrease in encapsulation efficiency. 29,33 From the above results, it is evident that the self-limitation in interfacial polymerization of polyurethane is the principal factor that restrains the increase of the microcapsule shell thickness. To increase shell thickness, a sufficient amount of monomer is needed, and delaying phase separation allows more monomers to meet at the oil−water interface before in a short time and participate in interfacial reactions, generating more oligomers.…”

“…32 Maruyama et al increased the shell thickness by increasing the proportion of TDI monomer concentration and obtained a thicker shell of 0.35 μm, which increased the cumulative release time of microcapsules from 1 day to 25 days. 33 Paret et al used polyurea as the microcapsule shell and fragrances as the core material, and shell thickness microcapsules were doubled by increasing the initial concentration of shell monomer concentration in the oil phase. When the original wall thickness was doubled, the cumulative release of encapsulated fragrances into the release medium decreased from 20% to near 0 in 25 min.…”

“…The shell thickness of microcapsules directly affects the release rate of microcapsules as the release of encapsulated core materials is basically molecular diffusion, which is inversely proportional to the shell thickness. , Furthermore, microcapsules with a thicker shell can also improve the thermal stability of microcapsules . Maruyama et al increased the shell thickness by increasing the proportion of TDI monomer concentration and obtained a thicker shell of 0.35 μm, which increased the cumulative release time of microcapsules from 1 day to 25 days . Paret et al used polyurea as the microcapsule shell and fragrances as the core material, and shell thickness microcapsules were doubled by increasing the initial concentration of shell monomer concentration in the oil phase.…”

Interfacial Polymerization Depth Mediated by the Shuttle Effect Regulating the Application Performance of Pesticide-Loaded Microcapsules

“…It has been reported that two methods of in situ and interfacial polymerization were employed to prepare fosthiazate-loaded MCs. 18,19 Presently, interfacial polymerization stands as the most industrialized technology for microencapsulation because it possesses advantages of simple process, fast reaction rate, and suitability for continuous production. 20−22 However, there is currently a dearth of straightforward and efficacious methodologies for encapsulating fosthiazate to obtain a stable preparation.…”

“…Currently, registered microcapsule (MC) preparations containing 20% and 30% fosthiazate are utilized for the management of root galling nematodes in China. It has been reported that two methods of in situ and interfacial polymerization were employed to prepare fosthiazate-loaded MCs. , Presently, interfacial polymerization stands as the most industrialized technology for microencapsulation because it possesses advantages of simple process, fast reaction rate, and suitability for continuous production. − However, there is currently a dearth of straightforward and efficacious methodologies for encapsulating fosthiazate to obtain a stable preparation. Achieving complete encapsulation is crucial for fabricating microcapsule preparation, enabling controlled release of the core material, and effectively enhancing application efficacy. , …”